Implement Track mode (Phase 6) with rotctld server

TUI-compatible Hamlib rotctld TCP server that works with the
existing SerialBridge/DemoDevice interface. F2 Control's Track
tab now starts/stops a real TCP server on the configured port.
Status callbacks report connection state, move count, and command
rate back to the TrackingPanel via thread-safe call_from_thread.

Includes 7 pilot tests exercising the full protocol path through
asyncio TCP clients against the DemoDevice.

tui/scripts/take_screenshots.py

@@ -0,0 +1,34 @@
+"""Take screenshots of all TUI screens in demo mode for documentation."""
+
+import asyncio
+
+from birdcage_tui.app import BirdcageApp
+
+SCREENS = {
+    "f1": "dashboard",
+    "f2": "control",
+    "f3": "signal",
+    "f4": "system",
+}
+
+OUT_DIR = "/home/rpm/claude/ham/satellite/winegard-travler/site/public/screenshots"
+
+
+async def main():
+    for key, name in SCREENS.items():
+        app = BirdcageApp()
+        app.demo_mode = True
+
+        async with app.run_test(size=(120, 40)) as pilot:
+            await pilot.pause()
+            await pilot.press(key)
+            await pilot.pause()
+            # Let workers populate data.
+            await asyncio.sleep(1.5)
+
+            path = f"{OUT_DIR}/tui-{name}.svg"
+            app.save_screenshot(path)
+            print(f"Saved {path}")
+
+
+asyncio.run(main())